Power factor regulator with under-voltage protection



March 16, 1954 D. v. HoTsoN POWER FACTOR REGULATOR WITH UNDERVOLTAGE PROTECTION Filed Nov. 13. 1951 lllllllllllllllk 4,5 co/vsr'A/Vr VOLTA@ TRANS/TOWER Il IHHIIIH v"stability limit. Heretofore, some systems utilized Patented Mar. 16, 1954 UNITED STATES POWER FACTOR REGULATOR WITH UNDER- VOLTAGE PROTECTION Application October 13, 1951, Serial No. 251,237

5 Claims. (Cl. S22- 20) 1 Z This invention relates in general to electric Fig. 1 diagrammatically illustrates the circuits regulating systems and in particular to means for and apparatus of one embodiment of the invencontrolling an electric circuit to limit the magnition, and tude of an operating condition thereof. Fig. 2 partially illustrates the circuits and ap- COIltiOl SYStelnS are lnOWn in Which a Ieg- 5 paratus of an alternate embodiment of the inlator which is normally operative to maintain Verisign constant an operating condition of an electric Referring to Fig. 1 one embodiment of the inrcut, such as Voltage, Current, speed or power vention is illustrated in connection with the conaCtOI, iS OVeFCOme by the action of means retrol of an alternating current circuit represented SDOIlSiVe t0 anOtheI Operating COI-lditOn Of the 10 by conductors 6, l', 8 to which is connected the Circuit attaining a limiting Vallie- When Synarmature lia of a synchronous dynamoelectric chronous dynamoelectric machines are connected manning li having a eld winding l lb. Field toen electric Circuit and the Opel-ting Cenditien Winding lib is supplied with excitation current being regulated iS the DOWeI' feCtO 0f the Circuit, from any suitable source such as the armature it is desirable to provide some means responsive 15 g2@ of a main exciter generator I2 having a field to the Voltage of the circuit for overcoming the Winding 5211 Field Winding i227 is in turn suppower 'factor regulator when the circuit voltage plied with Current from the armature |3a of an decreases to a predeterminedv critical value to 'amplifying exciter generator I3 having field prevent the power factor regulator from decreaswindings 13b, g3@ F1916; Winding |319 is @mb ine the machine excitation below the Synchronous 2o nested across armature le@ in series with' an adjustable resistor it to provide a variable amount oi the excitation for generator i3. Control field winding |30 is connected to be energized by a measure of the conditions being regulated.

If it is desired to maintain a constant power factor in conductors 5, l, 8, suitable means are provided to supply to field winding I3c a control voltage dependent upon this power factor. Such means may include potential transformers I t 3o having primary windings [6a connected to oonductors t, 1, il as shown and having a pair of secondary windings ith, itc connected to autof Whlch 1S Operatlve upon a Predetermmed under' transformers i?, lili, respectively. The voltage Voltage Condition of the cn'cuit to prevent the between the adjustable taps of transformers l1, machine excitation from decreasing below a pre' 'f' Hl is impressed across an additional autotransdetermined value independently of the operation formel. I 9 to produce thereacross a Voltage which 0f th? power factor regulttton is a measure of the voltage of conductors Si, 1, t.

It v1s therefore an obiect of this invention to A pa). of Quarant transforme 2! 22 are com protvide a new and improved electric regulating nested in Chcut with Conductors, g, respec; sys ein? It is an additional object of this invention to tu itsapgfroeacflttcn; provide an improved System for an electric cir' e, i 8. Resistor 23 is connected between the cuitprovlded Wlth .regulamtg means for maui' center terminal of transformer it and the center tammg Gr.18 optratmg condltlon of the clrcmt ,terminal of the primary windings 25a of isolating constant, in wh1ch system the operation of the tmnsformers 25 regulating means is abruptly overcome in re' :ciecondary winding Zlib of transformer 25 is Sponse to tnothet tteratng condition of the cir' connected to the alternating current terminals Cult tttammgahmftmg Value' of a full wave rectifier 26 having its direct cur- It is a further obJect of the present invention to rent terminals connected to a resistor M Sec Provide undervoltage TESPOnSVe means for a 50 ondarywinding 25o is similarly connected to a power factor regulator having no moving parts. :fun Wave fctel- 2g having a resistor 29 con..

Objects and advantages Other than those Set nected across thedirect current terminals there# forth above will be apparent from the following of. Resistors 2i, 2e have a common terminal, description when read in connection with the acthe connections of rectifiers 2a are suc-n companying drawing, in which: 55 that the voltage appearing across the noncommon ATENTy OFFICE a relay operative upon the circuit voltage attain- 4ing a critical value below the normal voltage vfor -recalibrating the power factor regulator to prevent the regulatorfrom decreasing the excitation .i5 of the machine below the stability limit. However, the operation of this system is slow owing to the presence of the mechanical elements, is subject to faulty operation and requires'maintenance of the mechanical elements.

' These disadvantages may be overcome by utilizing means having no moving parts and terminals of resistors 21, 29 is proportional to the diierence between the average values of the voltages of windings 25h, 25e.

The connections of transformers I6, I1, I8, 2| and 22 are such that the voltage across resistor 23 is in quadrature with the voltage across the outer terminals .of .transformer .I9 ,when-.machine I I is ope'xiatinggatithe 'desired power factor.. results in equal voltages being produced across secondary windings 25h, 25e so that under these?. conditions the voltage across the noncommon terminals of resistors 21, 29is'2zero.

This invention provides means responsive` to` the voltage of conductors .Ii.1Beintheaformeof a nonlinear resonant networkil; may be energized by a measure of the voltage of conductors 6, 1,. 8 through a ,potential trans.- former 35 and through a booster"transfonner"`31 energized from an autotransformer 36.v Network: 32 comprises a magnetically saturable device of suitable .typel having a winding connected lneries with a capacitor.v Such devicemay cnnsist of a saturabl'e transformer 33 having a pri mary winding 33a. connected .in series with a capacitor" 3l. i

"Transformer 33"has a secondary windingl33b, the..vu1tage, of which. is proportional tothe voltageof. Nvndngja, connected .to .the .alternating current' .terminals off. a iull wave rectifier 3,8 havinelits direct current terminalsconnectedto armesistorli. `Capacitor 34 is V,connected through afrr-isistol.v 40..to thealternating current terminals Qi..a...rectifier;-'4;I..having .a .resistor 42. connected acrossgthe .direct current terminals thereof; .1Resistors l3ii,.l42,.are providedlwith acommon termi.-

andowng.v toithe 4connections. ofrectifiers J38, 41 .thecontrolivoltageappearing across the `nom commouterminals. of.' resistors 138, 42 'is `proper` tlonalto the difference betweenthe average values Qlthe voltage, .ofwindingaand the voltage of captOrSI-IA.. A reactor 15II vandya rectiier'l may be. serially. connected across .the .noncommon-.terminals .0I .resistors 3.9., 4.2tolim'it thevo'ltage of 'fa predeterminedI4 polarity appearingacross these noncommonterrninals.

Thiscontrol lvoltage isimpressedon the control l' windingjMb. of a polarity` sensing device ofany Suitable type 'such as. va self-saturated' magnetic amplifier 4'4 havinga pair o`f;saturable cores 44a and. a reactance wind'ing44c. .Reactancefwindf ing.,4.4.c is supnl'iedwith .current from a suitable source of .substantially constant voltage such as a., transformer 45 connectedto conductors"`1'8 andjis ,connected .to ,thev alternating current l terminals .oi .a full' wave rectier 4'6 .through a Ipair ofjlialf-wave rectifers41, 48. Aresistor 49 is connectedto .the direct currentterminals .of rectiier '4.6 to.. .hai/@impressed thereacross an 44ont.- nutv ,voltage dependent .upon the` saturation, oi amplifier 44; Resistor 4.9 Tisconnectedin circuit withresistors .21, .23..in the circuit ,oijneld "windi118 [3a to. control the. excitation of machine Il iniresppnse, to, variations in .the above mentioned .output .and .control voltages.

In operation, assuming that the..voltage. of conductors 6, 1., is normal, and thatresistor. I4 isdjilsiied.. so that vfield Winding :13b .supplies .all of the excitation required to maintain the voltage.,of"armature I3a at any. given value, the poweriactor measuring circuit described yalcove ,operates to produce. across .thenoncommon ter,

minals .0I A4'resistors :21. 29 .a reversible .unidirec tional. .control voltage havinga -polarityiandmagnitude .dependent :uppnthe directionsnd man1: oi' variations the power .rector 01.-.

Network Ni ductors 6, 1, 8 from a predetermined value. This control voltage is impressed on eld winding I3c to change the excitation of field winding IIb in a direction to return the power factor of the circuit to the desired value.

Network 32 is so designed that when the volt- ...agerof-laonduotors 6, 1,.,8iisiabuueraf critical mini- ;mum value, transformer i3! satumteazover the greater part of each cycle. That is, network 32 :resonates during some part oi each cycle at the critical minimum value of the circuit voltage aandresonatesiuriiiga different part of each cycle attiie'ncnnal value of the circuit voltage, so that attnnrmalfcircuitnvnltage the average voltage of iaoapaniim Mexicaans the average voltage of winding 33h. Tliureln, the voltage of rectier 4I .andresistor 42 exceeds the voltage of rectier 38 `an'dresistofi'Y'toimpress across control winding Mbialcontrol voltage of a predetermined polarity. However, the poling of rectiiiers 41, 48 is so chosen that.. themagnetomotive force .produced bwfithis voltegefdoes .not increase .the output-murrent .through reactancx-i. vwinding .44c, so that his output currentzhasmnegligible value.` sultsA in .a negligible.. output voltage. beingolm- .pressed..across.:resistor 464mm .rectifier 46, `so thatthe .voltageresponsivemeanahasa negligible upon the r.regulating..system runderathese conditions.

.Ifi .the Avoltage of.. conductors :6, 1, .8z decreases withoutan accompany-ing... changeiin/.the excite tion. of` ,machine ..I.I,..ma.chine I'I- operatesfovorf .excited `.in comparison to. the way. itwopereted before. .the armature voltage-decreased. Under lthis.condition, .the power .-iaetor.- regulator `will vtendtereduce .the-machine. excitation rte correct .thei..overexcitedi.conditionl. Itffthe .power factor .regulator .decreases .the .machine excitation nto too ,.greatfamextenty .thefmachine .mayclosessym .chron'ous.stability-andpullriouttosten .'ro'ipref ventfsuch action, .the voltage responsive fnetwok .producesfasignal-tending-:to .increasethemachine excitation.

When theicircuitwoltage decreases toa 'critical minimum value, :the .voltage.vofafseoondaryfwindluga-3b exceedsithevoltageofncapacitor $34. .This actionreversesthe polarityol' .thecontrol volt rage. fappearingvaorossthe Y.nonoommon .terminals of lresistors 13a, 42 .and .across control winding 4411. This control voltage1f.is:-tben. ref thef inolarityf ite rincreasethe-outputcurrentlo! amplifier 44, .therebygproducdngraisubstantial voltage across :resistor 48.. 'Ime.aotionnticontrol,windingMbfisrincreaaed ,bye the-.ifr-saturating action of .1 windings 04e, so fthat'iafamali s control voltageimpressed across control winding Hb. .prlicluces-van^ sulisimxtialv fout'- put voltage across reiuetorv;y ouonutiwcl'b .agefrisiot-.arpomty-:to increase .themitattouzoi mcisimeefihmdifoveewmw appearing across resistors 21, 29 to inorealwthl lmachmeeexcitatiom power: twturfuegulocisfmrvvmd from: decreasing: theamachme: Vexcitation beim theastabrlitwlimtt The 'voltagecchaaugeaawm rlatvwilrlrf4 '32 `fwl'liclff. is required: torproduceamoe meneer isimfyrsmal'llfsnthiat thercxrltcal minimum value .of woltage of ttm-ficircuet may? vbeeaocunteiy controlled. The voltagefofrconductwsfft .1.; IVM which networkzqrewnatesyem thecritieallminimum. voltage at which theundervwago protection V.system reparation. .betadustednhy adjustment Aolf.. .31

. Eigen im' snelmenu: weinenden and`resistr aU'are rlixiniatee.;4 RectiersfBLll have-one pair of direct current terminals of like;

polarity connected together and have the other direct current terminals connected directly to resistor 49. Resistor 42 is connected across the direct current terminals of rectiiier 4i, as in Fig. 1.

When the voltage of capacitor 34 and rectifier 4| exceeds the voltage of Winding 33h and rectifier 3B, no current flows through resistor 49 from rectiiier 4I, since rectiiier 38 blocks such flow. However, when the voltage of winding 33b and rectifier 38 exceeds the voltage of capacitor 34 and rectifier 4l, current ows from rectiiier 38 through resistors 42 and 49 back to rectifier 38 to produce across resistor 49 a voltage tending to increase the excitation of machine Il. Thus, the embodiment of Fig. 2 operates in a manner similar to that of Fig. 1 to overcome the action of the power factor regulator when the voltage of conductors 6, 1, 8 decreases to a critical minimum value to increase the excitation of machine I I.

Although but two embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims. Features of the nonlinear resonant network disclosed herein are claimed in the application of Daniel J. Sikorra, Serial No. 114,751, iiled September 9, 1949. v

It is claimed and desired to secure by Letters Patent:

l. In a system for maintaining an operating condition of an alternating current circuit substantially constant at a predetermined value, the combination of a pair ci resistors, means respon-` sive to variations in said condition from said pre.- determined value connected to said resistors for producing in said resistors opposing voltages dependent upon said operating condition so as to produce across said pair of resistors a iirst reversible control voltage equal to the difference of said opposing voltages, voltages being equal only when said operating condition has sai-fl predetermined value, whereby said irst control voltage has one polarity when said variations are in one direction. and the opposite polarity when said variations are in the opposite direction, a nonlinear resonant network energized by a measure of the voltage of said circuit, said nonlinear network comprising a magnetically saturable device having a winding connected in series with a capacitor for producing across capacitor a voltage which varies abruptly at a critical Value of the voltage of said circuit, means including rectifier means connected to said network forv producing a iirst voltage proportional to the voltage oi said winding and a second voltage proportional to the voltage oi said capacitor, means for opposing said iirst and second voltages to produce a second control voltage dependent upon the difference of said iirst and second voltages, means for suppressing the diiierence of said first and second voltages when said second voltage exceeds said rst voltage, and means responsive to said iirst and second control voltages for controlling said condition.

2. In a system for maintaining an operating condition of an alternating current circuit substantially constant at a predetermined value, the combination of a pair of resistors, means responsive to .variations in said condition from said predetermined value connected to said resistors for producing in said resistors opposing voltages dependent upon said operating condition so as to produce across said pair of resistors a iirst reversible control voltage equal to the difference of said opposing voltages, said voltages being equal only when said operating condition has said predetermined value whereby said first control voltage has one polarity when said variations are in one direction and the opposite polarity when said variations are in the opposite direction, a nonlinear resonant network energized. by a measure or" the voltage of said circuit, said nonlinear network comprising a magnetically saturable device having a winding connected in series with a. capacitor for producing across said capacitor a voltage which varies abruptly at a critical value of the voltage of said circuit, means including rectiiier means connected to said network for producing a iirst voltage proportional to the voltage of said winding and a second voltage proportional to the voltage of said capacitor, means for opposing said rst and second voltages, means including magnetic amplifier means for producing a second control voltage dependent upon the difference of said first and second voltages, said magnetic amplifier means having a control winding energized by the difference of said first and econd voltages and an inductive winding connected to said circuit, means for suppressing the difference of said first and second voltages when said second voltage exceeds said first voltage, and means connected to said resistors and to said inductive winding so as to be responsive to said rst and second control voltages for controlling said condition.

3. In a system for controlling an alternating current dynamoelectric machine connected to a load circuit, the combination of a pair of resistors, transformer means connected to said circuit for producing a pair of signal voltages dependent upon variations in the power factor of said machine, rectifier means connected to said transformer means and to said pair of resistors for producing in said resistors opposing voltages dependent upon said signal voltages to produce a first reversible unidirectional control voltage equal to the difference of said opposing voltages, said opposing voltages being equal only when said power factor has a predetermined value whereby said rst control voltage has one polarity when said variations are in one direction and the opposite polarity when said variations are in the opposite direction, control means responsive to said first control voltage for controlling the excitation of said machine to maintain the power factor of said machine substantially constant, a nonlinear resonant network energized by a measure of the voltage of said circuit, said nonlinear network comprising a magnetically saturable device having a winding connected in series with a capacitor for producing across said capacitor a voltage which varies abruptly at a critical value of the voltage of said circuit, means including rectifier means connected to said network for producing a iirst voltage proportional to the voltage of said winding and a second voltage proportional to the voltage of said capacitor, means for opposing said first and second voltages to produce a second control voltage dependent upon the dinerence of said rst and second voltages, means for suppressing the difference of said first and second voltages when said second voltage exceeds said iirst voltage, and means for impressing said second control voltage on said control means to overcome Asaid iirst control voltage when said circuit voltage drops crtlearavaluefor fzincreasiwgrfthe excita tronic saldimachine.:v

4mm .ai system :.fortcontrolline anni aiternatingf coment dynamoeieotrlc .timacmnerconnected to a load eircuiti-thecombination f "apair otreeV sisi-:ora: Luisiana` connected .tto frsaidiE circuit 'and' f to saidlpairrotresrstors. forfrproducing inrusai'd re-r sisters?" opposing voltagesdependent f uporravaris: avionsf-rinz tliepowerriactorrrof saidwmachine itc orodircef acrossl saiclfpair.y oliresstorswaA L nrst'ffreL verslble @unidirectional .1 control: 2 voltage' equal to me' fdiile'rencefl of said (morning:r voltages; 'said voltages equal fonlyuwhensaidlpowcrffactcr nanevoreoetemmedvalue whereby said first con@ voltage has sono ipolarity ywhen said varia aref- `in one Adirection and` the f opposite pelanty'tvnensaid variations fare :inthe opposite direction, controlf means resioonaive ato said f controllvoitaee foricontrolling tnefeileitatlon of midfmecnine to 'maintainltne powerl factor 'ot said-machine 'sulostanlt'ially` constant, a nonlinear network energized `-ioy a measure fof the voltage.' of rsaid" circuit; said" netwcrlrV compris; me" a*magneticalliyfsaturabie device having Ia' winding connected "in series "with" a capacitor 'for orodcing across sani'capacitor avoit'age which vaesfabruptlyat 'a critical valueof the voltage ofvsaid icicult," I means including rectifier means comectet A'said''capacitor "and to said Winding fcrprodncing-anistvoltage proportional to the voltage ot said" winding and second voltage proportional "to "the voltage of said capacitor, means rr'opposing-@said nist and' second-voltages to Yproduce a second control voltage dependent uizio'rl'i tlie'dirence' ofsa'id first fandsecondvoltages, means for suppressing fthe-difference of @said first *and second voltagesvvhen said second volte age exceelis-saidinrst voltage; `means 'for iin-l oressnre Asaid control means esai-'cli' secondi-com v trol voltage toca-'use said' second 'control fvol'tase toovercome said first control 'voltage to increase excitation of said machine-'When the voltage oi' said eircom-drops to said'l critical lvalrei i5." in' a' systemv "for controlling ran faiternatilig' current dynarnoel'ectric machinefconnectedto a' loadcirouiit the combination of a pair offre sisters, means' 'connected *to rsaid circuit" and toy said pa-ir fof resistors for Tprodll'eine in'- `said 7 resistors opposing' vol-tagesA 'dependent uponl the 'said lpair ci? resistors v`a 'first `reversilile urlidirerji tional con-trol voltage equal to "ftliefdi-ference or &a scid opposingrvoltegesiisaidfwitagesibeinsiequet only when said Cpowerlectorrhaaazpredetermmed value :wherebyrsaidmrst controli `voltage has fone polarity whenrsaidzzvariations fi are ein one directionziancl T'the 2 opposite polarity :'whiexresaid wmf-l#V ations are in the opposite direction, control meansresponsiverto 'said vllnmtlcoutrol' rvoltage y"for i controlling .the excitation.' of '.s'aidf'machinefto maimtulnf ithe powr'ffactoriot saldi'. machine substam tie/lily constant; .a nonlinear: resonant network? energized by :a1 measure oll they voltage -off said circuit; saidvnetworkl :comorisineV aLA magnetically saturable "device fhaving .a WindingL connected soriesliwitn :a capacitorE forproclcinel across said' capaeitora :voltage nwhich5 varies` abruptly' atiacritbal 'valu'o'V or thevoltage of said-foire c'lt; sa-id' critical `valine ib'elnga`= predetermined amount :belwthe l normal -voltage f of-fsaidf circuit, means `including rectiilermeansr connected to said'jcapacitor fami to said-'winding for iprodiicirlsf a nrstfvoltagefproportional to the voltage oi saidfwi'nillng` and a second voltage proportional to the jvoltage `^`of "said capacitor; means forceps posingfsald nistf-andfsecond voltages, means im cIudi-ng magnetic amplifier f means forl producing a secondl controlf voltage-'dependent upon the difference or saidy first 'and second voltages; said magnetic Yampliii'er means having-'a control- 'winding energizedfbythe difference of said lil'rs't =and second voltages and"aninductive winding-com nected to said circuit, meansifor'suppresslng the diierence `of said f hrst" and second voltages when said second voltage exceeds saidv first voltage, `andmeans 'fr conl'iecting"saidv control means to said inductive `winding Aior*impressing` said :second control voltage on saidcontroi means to causesaid' output `voltageto overcome said frst controivoltageto increase the excitationl of said' machinewhenthevoltage 'of saidcircult drops tov said critical value;

DALE`V.' HOTSON.

References "-Citedl in'the -Ile *of 'this patenti' STATES PATENTS 

